Heretofore, retainers have been well known for use in the treatment of orthodontic patients following the removal of fixed appliances for the purpose of retaining the positions of the teeth. Such an appliance is removable and worn by the patient in accordance with instructions given by the orthodontist. While retainers are known for use on anterior teeth only, they are more well known for use on teeth of an entire arch, whether that be upper or lower. A retainer for the entire arch includes an acrylic lingual portion that is custom fit to generally engage the undercuts of the teeth. Wire members are embedded in the acrylic and extend over all or a portion of the teeth to coact with the lingual acrylic portion for retaining the teeth in a desired position. The most well known appliance of this type is called a Hawley retainer. While Hawley retainers have been constructed with several variations as to the wire formations, it is always common to provide the lingual acrylic portion for general fit with the undercuts of the teeth on the lingual side. This fit is more critical for the lower teeth because they lean somewhat inwardly and not as critical for the upper teeth which lean somewhat outwardly.
Successful results from any retainer depend upon the cooperation of the patient, as the patient has the choice of wearing or not wearing the retainer. In the event that a patient fails to wear the retainer for a period of time, difficulty can be experienced in thereafter placing the retainer due to relapse of teeth positions. Heretofore, it has been known to accommodate relapse problems in the anterior by construction of an appliance with resiliently biased portions such as the retainer sold by TP Orthodontics, Inc. and identified as a Spring Aligner Plus. However, no heretofore known retainer has been constructed to accommodate relapse in posterior teeth, and that has caused the patient to choose against wearing the appliance if not worn for a period of time because of the inability to place the appliance in the mouth. It may also cause the orthodontist to reconfigure the lingual acrylic portion of the appliance in order to permit the appliance to be placed and accommodate the posterior relapse.
It has also been well known that during fabrication of an appliance having rigid posterior sections, difficulty is encountered in removing the appliance from the model on which it is made.